Heat supplying high-frequency apparatus



May 6, 1958 F.' LAPPE 2,8

HEAT SUPPLYING HIGH-FREQUENCY APPARATUS Filed July 11, 1952 4 Sheets-Sheet 1 v /[YYYY] k 2 Jiaez 07:

May 6, 1958 LAPPE 2,833,925

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F. LAPPE HEAT SUPPLYING HIGH-FREQUENCY APPARATUS Filed July 11, 1952 4 Sheets-Sheet 4 glbaed 1 2 ll H MII fl fllllll l M U HEAT SUPPLYING HIGH-FREQUENCY APPARATUS Fritz Lappe, Erlangen-Buchcnbach, Germany Application July 11, 1952, Serial No. 298,420

Claims priority, application Germany July 12, 1951 13 Claims. (Cl. 250--40) This invention is concerned with apparatus for applying high-frequency oscillations to objects or bodies with varying reactances. Such apparatus are used, for eX- ample, for warming biologic tissues in the treatment of ailments, and for drying various materials.

It is a characteristic of these apparatus that the reactances of the objects will strongly vary during the treatment. In medical treatment, the variations are chiefly due to alteration of the position of the patient with reference to the treatment circuit, and in the drying of materials, the variations are due to alteration of the degree of desiccation. Such apparatus, therefore, necessitate frequent retuning of the circuit, loaded with the object to be treated, to its high-frequency supply circuit, to keep constant the high-frequency energy applied to the object'undergoing treatment.

The invention provides means for avoiding these disadvantages.

A primary object of the invention is to provide a tuning device associated with the circuit loaded with the object to be treated. This tuning device is driven by a constantly running motor which is reversed depending upon an operating value of the apparatus reaching a characteristic magnitude, indicating an increase of the distance from the resonance position. The tuning to resonance is therefore continuously automatic, sliding so to speak into the resonance position and upon reaching the latter it fluctuates about such position and sliding back into the resonance position in case it should change. It is, therefore, no longer necessary to tune the treatment circuit manually after applying it to the object to be treated and likewise unnecessary to supervise the maintenance of the resonance tuning during treatment.

Another feature of the invention is concerned with the simultaneous utilization of two operating values of the apparatus, one of which attains a maximum value in the case of resonance, while the other attains a minimum value in the case of resonance, for controlling a motordriven tuning device of the circuit loaded with the object to be treated. A control value or criterion is thus obtained which sumces to control the tuning motor even with slight detuning relative to the resonance position, so that automatic readjustment is assured even in case of slight detuning from the resonance position. In addition, by considerable alteration of the control value or criterion, resulting from any deviation from the resonance position, reduces the need for switching means for interpreting such criterion for the control of the tuning motor.

The foregoing and other objects and features of the invention will be presently described with reference to the accompanying diagrammatic drawings. In these drawings,

Fig. 1 shows first, at the left, a self-exciting tube oscillator and inductively coupled therewith a motor-tuned treatment circuit; second, centrally thereof, part of the apparatus which initiates the control for the motor-driven United States Patent ice tuning device; and, third, at the right, circuit means for controlling the reversal of the tuning motor;

Fig. 2 diagrammatically illustrates the flow of a control voltage obtained from the oscillator circuit of Fig. 1, in dependence on the capacitance of a tuning capacitor included in the treatment circuit;

Figs. 3 and 4 indicate the course of the input voltage and the output voltage relative to time, in a circuit such as shown in Fig. 1;

Figs. 5a to 5 are diagrams showing, in Fig. 5a, the variation of the capacitance C of the tuning capacitor of Fig. 1 upon running into resonance position and its repose in such position; in Fig. 5b, the time dependence of the actuation of contact i of Fig. 1; in Fig. 5c, the curve of the control voltage ST derived from the circuit according to Fig. 1; in Fig. 5d, the curve of the control value st derived from the circuit according to Fig. 1; in Fig. 52, the time dependence of the actuation of relay MR (Fig. 1) for controlling the sense of rotation of the motor M; and in Fig. 5f, the time dependent operation of the motor in its left and right hand directions of rotation;

Figs. 6a to 6 show the course of the same values as in Figs. 561-51) incident to a change of the object to be treated, causing automatic retuning of the capacitance of the tuning capacitor and of the treatment circuit according to Fig. 1, which keeps the tuning of the treatment circuit within the resonance range; and

Fig. 7 is a diagram showing an embodiment of a circuit for reversing the direction of rotation of the tuning motor, which may replace that shown in Fig. 1.

In Fig. l, G indicates the oscillator tube; GK the frequency-determining oscillator circuit; BK the treatment circuit comprising the tuning capacitor C regulated by the motor M, and the output terminals 1 and 2; Ra and Rg indicate two series-connected resistors, Ra being in the anode circuit while Rg is in the grid circuit and is connected to the band-pass filter SG with the output terminals 3 and 4.

The motor M is connected to the circuit of the apparatus so as to run as long as the apparatus is switched on. Its direction of rotation is determined by a relay (MR in Fig. 1) which reverses the direction of rotation of the motor in case of any alteration in the operating condition of the relay. The tuning capacitor C comprises a stator and a rotor revolving through more than 360. Owing to the specific nature of the capacitance of the capacitor C the capacitor rotor can be adjusted for all possible loads until resonance between the oscillator circuit GK and the treatment circuit BK has been established.

At resonance, the anode current Ia, flowing in the direction of the arrow (Fig. 1) through the resistor Ra, is at its highest while the grid current Ig flowing in direction of the arrow through the resistor Rg is at its lowest. If the rotor of the tuning capacitor C is adjusted by a motor, when switching on the apparatus, the treatment circuit BK would periodically slide into the resonance position and slide out of it again. This would result in a periodically varying voltage ST at the output terminals 3 and 4, according to Fig. 2, yielding with each 360 revolution of the rotor of the tuning capacitor C the maximal value A (as indicated in Fig. 2), corresponding to the particular resonance position.

The voltage ST at the terminals 3, 4, shown in Fig. '1, is utilized to control the circuit shown in Fig. 1. This circuit, the output terminals of which are connected to the input terminals 3, 4 comprises an amplifier tube V. To its grid there are connected the resistor capacitor combination Ci, R, and contact i. The contact i is controlled by the cam N which is disposed upon the shaft of the motor M, the motor also driving the tuning capacitor C. As will be seen from Figs. 5b and 6b, the contact i is repeatedly closed and opened by the cam N, durng the adjustment of the capacitor C from its lowest to its highest value (rotation of its rotor by 360). The capacitor Ci is thus periodically connected to the control voltage ST through the resistor R. The capacitor Ci is in this manner given an impulse charge every time the tuning of the treatment circuit BK slides into the resonance position and is in impulse manner discharged 'when sliding out of the resonance position. Consequently, on charging, there is a positive impulse voltage at the grid of tube V and on discharging, there is a negative impulse voltage thereon. With the control voltage ST remaining constant between two actuations of contact i, no impulse voltage is generated at the grid (Fig. 3). In the anode circuit of the amplifier tube Vand thus at the output terminals 5, .6, a negative impulse voltage st (Fig. 4 is generated in case of a positive control impulse voltage 'ST at the grid, and in case of a negative control impulse voltage ST, a positive impulse voltage st is gencrated (Fig. 3) by differentiation of the anode voltage by means of the anode-connected capacitance-resistor combination of a low time constant.

These control voltage .impulses st are conducted to the circuit shown at the right of Fig. 1 by way of the input terminals. In the anode circuit of the gas triode GT is disposed the relay S in series with its resting contact s1. Connected to the anode voltage U of the gas triode GT there is a voltage divider Sp, to the midpoint of which is connected the polarized relay P and the capacitor Cp. In addition, the relay MR is connected to the anode voltage U by way of the make-break contact p of the relay P. This relay MR can be short-circuited by the contact p. Each alteration of the operating condition of the relay MR Will effect a reversal of the direction of rotation of the tuning motor M for the tuning of the capacitor C.

Relay MR deenergizes upon shunting of its winding by contact p and places its contact mr .into normal position. The motor M is now energized over its field winding F and caused to rotate in left hand direction of rotation. Reenergization of relay MR has the opposite effect, namely, contact mr will be placed in operated position to cause the motor to rotate in right hand direction of rotation, by energization of its field winding F By a positive control voltage impulse st, that is, each time the control voltage ST decreases due to the coutinuedrotation of the capacitor C1, thereby causing the tuning of the treatment circuit BK to slide out of resonance, the gas triode GT is started, the relay S is momentarily energized and its make-break contact s2 is actuated to assume its operated position. The polarized relay P is thereby momentarily connected in parallel with the capacitor Cp and likewise momentarily energized, thus placing its make-break contact p into alternate position and thereby short-circuiting the motor control relay MR. Simultaneously with the opening of contact -s1, the anode current for the gas triode GT is interrupted and the relay S is -deenergized, placing its contact S2 into the initial position shown. The make-break contact p is however still in its alternate operating position. Accordingly, the capacitor Cp is charged.

The reversal of the direction of rotation of-the motor M causes the tuning of the treatment circuit BK to slide again into resonance. The control voltage ST is thereby increased again and the capacitor Ci is recharged and at the output terminals of the circuit as well as at the input terminals of the right hand circuit portion of Fig. 1, there are negative control impulses generated, which are not able to start the gas triodeGT. The motor M continues running in the adjusted direction of rotation until the tuning has passed the resonance position, after which the control voltage ST drops thus again releasing the operations for reversing the direction of rotation of the motor.

Accordingly, so long as the object treated maintains its 'reactance during treatment, the tuning of the treat ment circuit will fluctuate about resonance position as indicated in Fig. 5.

Figs. 5a to 5) illustrate the operation of the apparatus during a time extending from the instant of starting operation outside the resonance range to the fluctuation of the tuning about resonance position. The operation of each of the essential switching elements at any instant will be apparent from Figs. 5a to 5 Upon starting operation responsive to placing current on the apparatus, the motor M (Fig. 1) willstart rotating in right hand direction of rotation, relay MR being energized (Fig. 5f). The capacitance of the capacitor C which is driven by the motor, increases, as indicated in Fig. 5a and the cam N closes contact i (Figs. 1 and 5b) periodically during each revolution of the motor. The motor requires some time to come to its full rated R. P. M. (Fig. 5)) and the contact i is therefore initially actuated in larger and gradually decreasing operation increments, until it is actuated with uniform spacing when the motor M reaches full speed.

As shown in Fig. 2, the control voltage ST derived from the increase of capacitance C (Fig. 1), is changed only upon approximation of the tuning to resonance position, reaching its highest value (Fig. So) at the resonance point, with the capacitance C (Fig. 5a). With increasing control voltage ST there will be produced, at the output of the circuit Fig. .1, right hand end, negative impulses st (Fig. 5d) due to periodic closures of contact i. Upon first closure of contact i (Fig. 5b), after overstepping the resonance point, the capacitance C (Fig. 5a) will have increased, but the control voltage ST (Fig. 5c) has decreased due to the drop in the operationally effective degree for the load transmission of the oscillator circuit to the treatment circuit, which degree is most favorable only in the resonance point. The impulse st (Fig. 5d) therefore becomes positive, the relay MR will restore (Fig. 5e) and the motor M is switched over (Fig. 5f).

After this switching over, the capacitance C Wlll decrease and the tuning will accordingly again near the resonance point, resulting in an increase of the control voltage IST. Upon next closure of contact i, a negative voltage value st will again result, the relay Mr remains normal, 'the motor will continue to rotate in left hand sense, so that the resonance point is finally again overstepped, by further decrease of'the capacitance C, whereupon the control voltage ST decreases again (Fig. 5c), causing the impulse st to become positive again, responsive to next successive closure of contact 1, thus resulting in energization of relay MR and consequent switching over of the motor to rotate in right hand sense.

The tuning to resonance position is in 'this manner effected automatically and so long as the treated object retains its reactive or base resistance, the tuning of the treatment circuit will fluctuate about the resonance position.

if the reactive resistance component of the object undergoing treatment changes gradually within the time 2 to t (Fig. 6a) in such a manner as to cause dropping oi the resonance value from C to C and then C the tuning will be effected automatically to the resonance position by fluctuations about the intermediate resonance point 'C and will fluctuate about the new resonance position C which is due to'the fact that gradual drop of the resonance value occurs during several actuations of contact i (Fig. 6b). 'Th'e'operation is indicated in Fig. 6a by the full line,'the dash line indicating the capacitance curve required for the corrective tuning to which the actual capacitance curve is well matched. From Figs. 6b to-6f may be had the closures of contact i (Fig. 6b), the

. changes in the control voltage ST (Fig. 6c) and the conthe motor M in right and left hand sense, respectively, incident to capacitance variations according to Fig. 6a.

The motor control circuit shown in the right hand end of Fig. 1 may be replaced by the one shown in Fig. 7. This latter circuit comprises merely two gas triodes, thus making it less expensive. Moreover, compared with the circuit shown in Fig. 1, it has the advantage of avoiding time lags such as are involved in the operation of the relays S, P and MR.

The circuit according to Fig. 7 is constructed so as to assure starting of one tube first, for example, tube Th1 incident to switching on the apparatus. A voltage drop is thereby caused at the cathode resistor Rk, which is common to both tubes. This voltage drop causes a negative bias of the grid of tube Th2, preventing the start of this tube. Upon starting the tube Th1, the motor M of the tuning capacitor becomes excited through its winding F which is connected to the plate circuit of this tube. An increase of the control value ST and a resulting negative control impulse st has no effect on the operation of tube Th1, since negative voltage impulses at the grids of tubes Th1 and Th2 cannot start the tube Th2. After the resonance position is passed, the control voltage ST decreases, as described above, and the positive voltage impulse st caused hereby starts the gas triode Th2. Since the capacitor Caa, connected to both plates of the tubes Th1 and Th2, is charged through the exciting winding F and the tube Th1, still connected-through, a discharge impulse occurs when starting tube Th2, which causes the voltage at the plate of tube Th1 to break down, thus interrupting the current flow in this tube. The motor M is now excited through the Winding F disposed within the plate circuit of tube Th2, and reverses its direction of rotation. The tuning now slides again into the resonance position, passes it, and slides out of resonance. In this case, another positive control impulse st occurs at the input of the circuit, starting the tube Th1 again and blocking the tube Th2, causing another reversal of the motor.

Instead of the gas triodes Th1 and Th2, two highvacuum electron tubes may be employed, to be operated in a known flip-flop circuit. The operation of the circuit is similar to that for the gas triodes. Since only plate currents are available when employing high-vacuum electron tubes instead of gas triodes, which are too low for motor excitation, a relay for reversal of the motor should be used, as employed in the circuit according to Fig. 1, marked MR. Changes may be made within the scope and spirit of the appended claims.

I claim:

1. High-frequency apparatus for treating objects with high-frequency oscillations, comprising a high-frequency current source and a load circuit associated with an object to be treated, to impart heat to said object; tuning means for tuning the resonance between said source and said load circuit; a motor for driving said tuning means, said motor rotating constantly during said treatment; switching means for controlling the direction of rotation of said motor; control means for governing the operation of said switching means depending upon an operating criterion which reaches a characteristic value upon establishing said resonance; control members in said control means for operatively releasing said switching means for the control of direction of rotation of said motor only incident to variation of said characteristic value of said criterion which indicates an increase of the spacing of said tuning from said resonance; means for actuating said control members for releasing said switching means for the control of the direction of rotation of said motor responsive to occurrence of a voltage which results from the diiference of the magnitudes of said criterion before and after the increase of spacing from said resonance; a capacitor constituting a control member for determining said difierence; circuit means for supplying to said capacitor a voltage which increases when approaching said resonance during said tuning and which decreases responsive to detuning from said resonance; electrical means connected with said capacitor constituting a control member for operative release of said switching means, said electrical means supplying a control signal for said switching means only incident to the discharge of said capacitor; directional relay means connected with said capacitor; said relay means being operatively energized only responsive to discharge of said capacitor; and means controlled by said relay means for generating a control impulse for actuating said switching means.

2. Apparatus as defined in claim 1, comprising an amplifying tube, means for connecting the grid of said tube with said capacitor, and electrical means controlled by said tube for generating a control impulse for the actuation of said switching means responsive to an increase of the voltage at the anode of said tube. 1

3. Apparatus as defined in claim 2, comprising a further tube having at least three electrodes, circuit means for controlling the grid of said further tube by the voltage on the anode of said amplifier tube, said further tube being adapted to initiate the generation of said control impulse by the increase of the potential on its control grid responsive to an increase of the voltage at the anode of said amplifier tube. v

4. Apparatus as defined in claim 1, comprising an amplifying tube, means for connecting the grid of said tube with said capacitor, and electrical means controlled by said tube for generating a control impulse for the actuation of said switching means responsive to an increase of the voltage at the anode of said tube, element for differentiation of the voltage at the anode of said amplifier tube, and means for connecting said element between the anode of said amplifier tube and said electrical means for the generation of a control impulse for said switching means responsive to an increase of the voltage at the anode of said amplifier tube.

5. Apparatus as defined in claim 1, comprising means for periodically momentarily applying said voltage to said capacitor, a cam driven by said motor, and contact means controlled by said cam for periodically momentarily,

applying said voltage to said capacitor.

6. Apparatus as defined in claim 1, comprising a fur-v ther tube having at least three electrodes, circuit means.

for controlling the grid of said further tube by the voltage on the anode of said amplifier tube, said further tube being adapted to initiate the generation of said control impulse by the increase of the potential on its control grid responsive to an increase of the voltage at the anode of said amplifier tube, said further tube being a gas filled triode which is started responsive to increase of the potential on its grid.

7. Apparatus as defined in claim 1, comprising a fur ther tube having at least three electrodes, circuit means for controlling the grid of said further tube by the voltage on the anode of said amplifier tube, said further tube being adapted to initiate the generation of said control impulse by the increase of the potential on its control grid responsive to an increase of the voltage at the anode of said amplifier tube, said further tube being a gas filled triode which is started responsive to increase of the potential on its grid, and a relay connected in the anode circuit of said triode in series circuit with its own winding.

8. Apparatus as defined in claim 1, comprising a fur-' ther tube having at least three electrodes, circuit means for controlling the grid of said further tube by the voltage on the anode of said amplifier tube, said further tuber being adapted'to initiate the generation of said control impulse by the increase of the potential on its control grid responsive to an increase of the voltage at the anode: of said amplifier tube, said further tube being a gas filled triode which is started responsive to increase of the potential on its grid, and a relay connected in the anode circuit -7 of said tried: in series with its o n n g; a Contact controlled by said r lay, :1 furt r polarized y. Circuit means inclpding said contact for energizing said polarized relay responsive to energization of said first relay, contact means actuated by said polarized relay for controlling the direction of rotation of said motor, said last named contact means being effective to prepare said polarized relay for actuation in opposite direction responsive to a successive control impulse therefor.

9. Apparatus as defined in claim 1, comprising a further tube having at least three electrodes, circuit means for controlling the grid of said further tube by the voltage on the anode of said. amplifier tube, said further tube being adapted to initiate the generation of said control impulse by the increase of the potential on its control grid responsive to an increase of the voltage at the anode of said amplifier tube, said further tube being a gas filled triode which is started responsive to increase of the potential on its. grid, a relay connected in the anode circuit of said triode in series circuit with its own winding; a contact controlled by said relay, a further polarized relay. circuit means including said contact for energizing said polarized relay responsive to energization of said first relay, contact means actuated by said. polarized relay for controlling the direction of rotation of said motor, said last named contact means being effective to prepare said polarized relay for actuation in opposite direction responsive to a successive control impulse therefor; a capacitor constituting a culrent source for said polarized relay, and circuit means for controlling the charging and discharging of said capacitor including a contact of said polarized relay.

10. Apparatus. as defined in claim 1, wherein said directional relay means comprises two relays of different energizing sensitivity, circuit means for connecting said relays in parallel at the input side thereof, each of said relays controlling a different field winding of said motor, said fieldwindings determining the direction of rotation of said motor, and means associated with said relays for effectingalternate energization thereof responsive to successive discharge operations of said capacitor.

11. Apparatus as defined in claim 1, wherein said directional relay means comprises two relays of different energizing sensitivity, circuit means for connecting said relays in parallel at the input side thereof, each of said relays controlling a different field winding of said motor, said field windings determining the direction of rotation of said motor, and means associated with said relays for effecting alternate energization thereof responsive to suecessive discharge operations of said capacitor; gas filled triodes constituting said relays, a common cathode resistor forsaid triodes, circuit means including a capacitance for interconnecting the anodes of said triodes, and a field winding of said motor connected in the anode circuit of each triode.

12; In a high frequency apparatus for the treatment -ofobjects with high frequency oscillations, having a high frequency current source and a load circuit associated with an object to be treated, to impart heat to said object; and-having tuning means for tuning the resonance between said source and said load circuit and having a motor for driving said tuning means, said motor rotating constantly during said treatment, and having switching means; for controlling the direction of rotation of saidmotorand control means for governing the operation of saidswitching means depending on an operation criterion whichreaches a characteristic value upon establishing said resonance, control members for producingcontrol impulses of changing polarity incident to "8 detuning from said resonance, switching means for controlling the reversal of the direction of rotation of said motor, said switching means being operatively effective solely responsive to said control impulses of changed polarity resulting from detuning from said resonance, means for actuating said control members for operating said switching means for the control of the reversal of direction of rotation of said motor responsive to becurrence of a voltage which results from the difference of the magnitudes of said criterion before and after the increase of spacing of said tuning from said resonance, a capacitor constituting a control member for determining said difference, circuit means for supplying to said capacitor a voltage which increases when approaching said resonance during said tuning and which decreases responsive to detuning from said resonance, and electrical means connected with said capacitor and controlled by the discharge thereof, said electrical means constituting a control member for the operative actuation of said switching means, said electrical means supplying a control signal for said switching means only incident to the dis charge of said capacitor.

13. In a high frequency apparatus for the treatment of objects with high frequency oscillations, having a high frequency current source and a load circuit associated with an object to be treated, to impart heat to said object, and having tuning means for tuning the resonance between said source and said load circuit and having a motor for driving said tuning means, said motor rotating constantly during said treatment, and having switching means for controlling the direction of rotation of said motor and control means for governing the operation of said switching means depending on an operation criterion which reaches a characteristic value upon establishing said resonance, control members for producing control impulses of changing polarity incident to detuning from said resonance, switching means for controlling thereversal of the direction of rotation of said motor, said switching means being operatively effective solely responsive to said control impulses of changed polarity resulting from detuning from said resonance, means for actuating said control members for operating said switching means for the control of the reversal of direction of rotation of said motor responsive to occurrence of a voltage which results from the difference of the magnitudes of said criterion before and after the increase of spacing of said tuning from said resonance, a capacitor constituting a control member for determining said difference, circuit means for supplying to said capacitor a voltage which increases when approaching said resonance during said tuning and which decreases responsive to detuning from said resonance, electrical means connected with said capacitor and controlled by the discharge there of, said electrical means constituting a control member for the operative actuation of said switching means, said electrical means supplying a control signal for said switching means only incident to the discharge of said capacitor, and means for periodically momentarily applying said voltage to said capacitor.

References Cited in the file of this patent UNITED STATES PATENTS 2,369,542 Dietrich Feb. 13, 1945 2,478,977 Nicholson Aug. 16, 1949' 2,499,967 Nicholson Mar. 7, 1950 2,508,321 Wilmotte Feb. 26, 1950 2,587,175 Lappin Feb. 26, 1952 2,705,286 Kinn Mar. 29, 1955 

